China is the top cyberthreat to the U.S. and has been intensifying attacks on U.S. businesses to identify data that will help the country gain economically, according to a recently obtained national security document.

Over the past five years, the Chinese have focused their efforts on businesses operating in finance, technology, and aerospace, among others, according to the Washington Post, which published information from the National Intelligence Estimate (NIE), a document that includes data and analysis from all U.S. intelligence agencies. The Post obtained information related to the report from unidentified individuals.

The cyberwar between the U.S. and China has been well-documented. The countries have not publicly said that they're targeting each other, but both sides have said that they're being hit with cyberattacks. It's also been widely believed that China has been attempting to access corporate information for its gain.

Interestingly, China might not be the only threat the U.S. faces. According to the Post, the NIE says Russia, Israel, and France have all conducted cyber-espionage efforts aimed at economic efforts in the U.S. Still, China's efforts are most frequent.

The NIE is one of the most secretive documents in the U.S. government and its existence has often been the subject of debate. In a statement to the Post, in fact, a spokesman for the Office of the Director of National Intelligence said that the agency does "not discuss or acknowledge the existence of NIEs unless directed to do so."